1. Field of the Invention
This invention relates to an engine, and more particularly to the structure of a Stirling engine.
2. Description of the Related Art
A conventional. Stirling engine is disclosed in U.S. Pat. No. 4,753,072. The Stirling engine disclosed in this document includes a condenser having a plurality of tubes provided in a housing, a regenerator and a cooler which are disposed between an expansion cylinder, and a compression cylinder. Each of the tubes of the condenser has a working gas, such as helium, located therein. Further, the condenser has sodium between the bundle of tubes and the housing. The sodium is heated and vaporized by an evaporator, and flows into the condenser in order to heat the working gas in the tubes.
However, in the above-described device, since the Stirling engine is provided with only one cooler, the working gas is ineffectively cooled down in the cooler.
Another Stirling engine, which is disclosed in Japanese Patent No. 51(1976)-10310, includes a heating tube, a regenerative portion and a plurality of cooling tubes. However, in this device, the working gas is ineffectively heated in the heating tube since the structure comprises only one heating tube.
To overcome the aforementioned problems, a Stirling engine can be constructed to include a plurality of heating devices and a plurality of cooling devices. However, this Stirling engine suffers from the drawback that the working gas flowing in all of the heating devices cannot be equally heated since all of the heating devices cannot equally receive the heat from a heat source due to the location of the heating devices in relation to the heat source. That is, the working gas flowing in the heating device located at a near position to the heat source is sufficiently heated by the heat source, but the working gas flowing in other heating devices disposed at distant positions from the heat source are insufficiently heated.
All of the unequally heated working gas flows into the regenerator, into each of the cooling devices and, as a result, into the compression cylinder. Thus, thermal energy of the working gas cannot efficiently be transformed into motive energy. That is, because the Stirling engine comprises only one regenerator, the measurement of the regenerator (such as the diameter or the length) cannot be adjusted according to the unequally heated working gas in each of the heating devices. Therefore, the Stirling engine is not able to increase the output torque.